Tom Cornacchia, a veteran mortgage-backed securities salesman at Credit Suisse First Boston, left the firm early last week to join Goldman Sachs. An ex-CSFB individual says Cornacchia covered some of the more active managers in the MBS market, including Clinton Group and WAMCO, and was considered a "big producer." He reported to Tom Guba, head of structured product sales at CSFB, who was traveling last Friday and unavailable to comment. A call to John Sobol, head of MBS at Goldman Sachs, was not returned at press time.